The compressor clutch is controlled by the body controller which is located in the left side kick panel

Andy3221 :

If the body controller is seeing low freon pressure in system or if one of the thermsitors are not reading temperatures properly in the system , it will not engage the clutch .

Andy3221 :

This is designed this way so as to not damage the compressor if all the freon was lost in the system

Andy3221 :

You can perhaps try cleaning the connectors at the thermistors to see if they are dirty and not making proper connection

Andy3221 :

this sometimes causes the body controller to not let clutch kick in

Customer:

I know we have a full charge in system, what voltage are we suppose to have at the thermistors?

Andy3221 :

How much freon is in system? in lbs?

Customer:

1.875 or 30oz

Andy3221 :

Good ! And system is free of leaks ?

Andy3221 :

Have you tried cleaning the connectors at the thermistors using an electrical contact cleaner or brake clean? And then , reconnecting them ? Sometimes helps ! Also clean the thermistors themselves and make sure pins are ok in thermistors !

Customer:

yes, it held a vacuum for more than 3o minutes. when we started it had some freon in it

Andy3221 :

The thermistors tell the body controller what temp the inlet evap line and outlet evap lines are and then , from that information decides whether to engage clutch or not

Customer:

have not tried cleaning any connections, i have pulled the connectors off he switches.

Andy3221 :

Check for corrosionand make sure little tiny pins inside thermistors are still intact ! There should be 2 in each thermistor

Andy3221 :

In many cases , replacing thermistors is the problem ! You may have one that is out of whack !

Customer:

i will have my tech try that in the am. how do i get back to you if that doesn't work?

Customer:

Can they be tested by jumping across them?

Andy3221 :

I work for an International dealership and can tell you that whenever I see these symptoms , 80 % of the time , it is a thermistor that is the problem

Andy3221 :

No , unfortunately , there is no way of fooling the body controller !

Andy3221 :

You have to pull freon out again to replace those two thermistors

Andy3221 :

I recommend replacing both while you are there and clean connectors and make sure they are ok too\

Andy3221 :

They are inexpensive

Andy3221 :

The worst part of all this is you have to pull freon out again to replace them !

Andy3221 :

Sorry about bad news

Andy3221 :

We have a laptop at work and we connect with special software to the body controller and are able to tell from the thermistor readings on that software wether they are defective or not and in many cases, that is the problem!

Customer:

thanks i'll try that.

Andy3221 :

Ok ! Good Luck !Please click on ACCEPT if my answer was satisfactory as this is how I get paid for my time and services !

Andy3221 :

I'll still be around to assist you further if needed! FEEDBACK AND BONUS are appreciated but optional

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